Fabrizio Dolcini
Tunable supercurrent
In collaboration with F. Giazotto from the experimental group at NEST in Pisa, we have investigated the Josephson Effect in a S-N-S junction (S=Superconductor; N=Normal) where the normal region is realized with a ballistic ring.
The underlying idea is that, when the N-region is a quantum interferometer, the supercurrent flowing through the S-electrodes can be manipulated by tuning the parameters of the interferometers.
It has been shown that, by exploiting the electro-magnetostatic Aharonov-Bohm effect in the ring, not only the magnitude but also the sign of the supercurrent can be tuned. The system thus represents a fully tunable pi-junction. The system can be implemented by realizing Aharonov-Bohm rings with semiconductor heterostructures; highly transparent contacts between a semiconductor and superconducting electrodes (such as Niobium and Aluminium) can be obtained with appropriate gradual doping of the former.
References
F. Dolcini and F. Giazotto, Switching the sign of Josephson current through Aharonov-Bohm interferometry, Phys. Rev. B 75, 140511 (2007)
F. Dolcini and F. Giazotto, The electro-magnetostatic Aharonov-Bohm effect as a tool to tune the Josephson current, Physica E 40, 2091 (2008).
